CHEM211 Lecture Notes - Lecture 12: Volumetric Flask, Magnetic Stirrer
10 May 2018
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FLUORIDE EXPERIMENT:
Materials
- Glass bottle
- Graduated Cylinder.
- 50 mL beaker
- 250 mL Volumetric flask
- Funnel Support
- Funnel
- Glass stirring rod.
- 4 x 50 mL volumetric flask.
- Plastic Bottle with Demineralized water.
Procedure.
1. Place 100 mL of TISAB in glass bottle, and add 500 mL of demineralized water.
2. Weight 0.11 g of NaF to the nearest 0.1 mg into a beaker.
a. Dissolve in 25 mL of demineralized water.
b. Quantitatively Transfer to 250 mL volumetric flask and dilute with TISAB solution made in
step 1.
c. Calculate exact molarity of NaF stock solution.
3. Pipet 10 mL of solution in step 2 into 50 mL volumetric flask → Dilute to volume with TISAB in
step 1.
4. Pipet 10 mL of solution in step 3 into a 50mL volumetric flask and dilute to volume using TISAB.
5. Pipet 5 mL of solution in step 2 into a 50mL volumetric flask and dilute to volume with TISAB.
6. Pipet 10 mL of solution in step 5 into a 50mL volumetric flask and dilute with TISAB.
REMINDERS:
-Clean Pipet
-Do NOT use more than 5-6 mL of solution to rinse the pipets!
-Wait time for recording values should be the same within +/- 7 seconds.
-REGISTER FOR
If you have an hour and a half left or more;
1. Take standards 2-5, the sample, five 50 mL beakers, wash bottle and a waste beaker.
2. Electrode needs to be conditioned for 3 minutes in solution #2 with meter on standby → Place 20
mL in beaker.
a. After 3 minutes, rinse electrode with clean demineralized water and blot away excess
water away with a kimwipe.
3. Begin measurements by taking least concentrated standard into a beaker, add stirring bar and
place beaker on magnetic stirrer set for gentle stirring.
4. With meter on standby rinse electrode tips with demineralized water, and blot excess water from
electrodes. → Immerse both electrodes in standard solution.
Obtaining a mV reading:
1. Press stby/meas key to activate the meter. Make sure it is in mV (Check manual if its not) and
reading to nearest 0.1 mV
2. Wait for two minutes then record value in notebook.
3. Press stby/meas key to return to standby position.
4. Rinse electrodes and stirring bar in waste beaker and blot dry.
5. Repeat steps 1-4 for the remaining standards and sample working towards higher concentrations.
6. Repeat set of five measurements a second time.
